Tobacco reconstitution

ABSTRACT

The invention relates to the extrusion of filamentary strands of reconstituted tobacco through a die plate and the downstream handling thereof. The die plate is configured such that each filament is of a square or rectangular cross-section, the downstream handling of which effects draw down of the extruded filament.

[0001] The present invention relates to tobacco reconstitution andparticularly to the extrusion of filamentary strands of reconstitutedtobacco. More specifically the present invention relates to thetreatment of filamentary strands of reconstituted tobacco downstream ofa tobacco reconstitution extruder.

[0002] There have been many prior proposals for the production oftobacco based material utilising particulate tobacco. According to theseproposals, the particulate tobacco may be tobacco dust inadvertentlyproduced during smoking article manufacturing processes, cigarettemanufacturing processes for example, or may be obtained by grindingtobacco leaf lamina or stem portions. The materials produced from theparticulate material may take the form of flat webs or sheets, rods,filaments or hollow cylinders. Processes producing these materials arecommonly referred to as tobacco reconstitution processes.

[0003] Components additional to tobacco which have been proposed forinclusion in materials produced by reconstitution processes are water;binding agents, e.g. pectin, starch, pullulan and cellulosic binders;fillers; humectants; expansion agents; reinforcing agents; andflavourants.

[0004] A prior proposed reconstituted tobacco process by the applicantwas disclosed in UK Patent Specification Nos. 2 201 081B and 2 201 080B.The process involved feeding a mixture of particulate tobacco, starchand binder, with the addition of water to an extruder to provide a sheetform extrudate, the extrusion being carried out under such conditionsthat the extrudate assumes a cross-section greater than that of the exitorifice of the extruder die, i.e. undergoes an expansion process. It wassuggested that it is advantageous to draw down the sheet form extrudate,so to effect an increase in the machine direction dimension of theextrudate and a decrease in the thickness thereof.

[0005] A further reconstituted tobacco process is disclosed in GB 2 291778B.

[0006] A disadvantage of the reconstituted tobacco processes describedin these patent specifications is that production of sheet material canbe problematic. For example, the thickness, strength and elasticity ofthe sheet material may be difficult to regulate and if any of theseparameters is outside of tolerance limits downstream manipulation of thesheet material (i.e. through cutters) can be adversely affected.

[0007] A further disadvantage of this prior art reconstituted tobaccoprocess is that once cold the resultant sheet product has an upper skinand a lower skin with a honeycomb structure therebetween. Thusdegradation of the product may occur at transverse faces of the product,i.e. faces not constituted by a skin. Thus the product is frangible. Itis, therefore, undesirable or practically impossible to pneumaticallyconvey such a product.

[0008] U.S. Pat. No. 4,632,131 discloses the extrusion of strands orfilaments of reconstituted tobacco wherein a plurality of strands areextruded from a die, comprising a circular array of exit orifices, andare subsequently adhered to one another so as to form a reconstitutedtobacco rod having passageways extending generally longitudinallythereof.

[0009] A disadvantage of such strand extrusion methods for reconstitutedtobacco, when it is required to produce discrete strands, is that thestrands exiting the exit orifices of the extruder die are difficult tohandle without the strands becoming co-adhered.

[0010] An object of the present invention is to provide an improvedmethod of manufacture of extruded, filamentary, reconstituted tobacco.

[0011] A further object of the present invention is to provide animproved method of handling an extruded, reconstituted tobacco filamentdownstream of an exit orifice of the extruder.

[0012] A yet further object of the present invention is to provide animproved filamentary reconstituted tobacco product.

[0013] An even yet further object of the present invention is to providea reconstituted tobacco product of appropriate dimensions forincorporation into a smoking article, i.e. a cigarette.

[0014] The present invention provides a method of handling an extrudedreconstituted tobacco filament downstream of die means through whichsaid filament is being extruded, wherein said filament is transferred ina direction longitudinal of said filament away from said die bypneumatic conveyance means, said conveyance means effecting draw down ofsaid filament such that the cross-sectional dimensions of said filamentare reduced.

[0015] Advantageously, the method may further comprise a cutting step,in which step the extruded filament is cut transversely at intervalsalong the length thereof into a plurality of elements. For example, thefilament may be cut at intervals in the range of about 10 mm to about 50mm. Preferably, the extruded filament is cut subsequent to the reductionin the cross-sectional dimensions of the filament. The cutting meansutilised in the cutting step may suitably be a rotary cutter.

[0016] Advantageously in some instances the method may further comprisea cooling step, whereby cooling air is brought into contact with theextruded filament to effect cooling thereof. The temperature of theextruded filament at the cutting means, when present, shouldadvantageously be low enough to ensure that the extrudate isinsufficiently tacky to cause problems in the operation of the cuttermeans. Suitably, the temperature of the extruded filament at the cuttingstage is within the range of about 20° to about 60° Celsius, preferablywith the range of about 30° to about 50° Celsius.

[0017] Preferably, the pneumatic conveyance means comprises a gaseousmedium transfer means and duct means, the transfer means being operableto cause transfer of gaseous medium, as a continuous flow thereof,through the duct means. The gaseous medium transfer means may comprise,for example, suction means, which suction means may suitably be providedby fan means. Preferably, the inlet end of the duct means is positionedadjacent to the extruder die such that when the filament emerges fromthe die orifice the filament is readily transferred in a directionlongitudinal of the filament away from the die under the action of thecontinuous flow of gaseous medium through the duct means. Advantageouslythe inlet end of the duct means is located within about 5 mm about 20 mmfrom the extruder die, and preferably within the range of about 10mm-about 15 mm. The transfer in a direction longitudinal of the filamentis advantageously initially perpendicular to the die face. Thereafterthe transfer may be in a substantially horizontal or vertical plane.

[0018] In normal practice the gaseous medium will be air, and thus aironly is referred to hereinbelow.

[0019] The draw down of the filament, to reduce the cross-sectionaldimensions thereof, is effected by the velocity of the air flowing in adirection which corresponds with the transfer direction of the filamentbeing greater than the extrusion velocity. Therefore, the filamentdownstream of the extruder die is tensioned and drawn down by the air.Draw down may be enhanced by tensioning the filament further by drawingthe filament over a tensioning means. The tensioning means may be, forexample, a driven roller.

[0020] Draw down is effected advantageously by an air velocity in therange of 60-180 m/s, and is preferably at least 100 m/s. The drawn downvelocity required is dependent on the formulation chosen and thethroughput selected in the extruder. The air velocity can be variedusing the suction means, the cross-sectional area of the duct, or both.The conveying velocity after draw down is suitably in the range of 30-60m/s, and is preferably at least 35 m/s, and more preferably in the rangeof 40-60 m/s.

[0021] Much to be preferred is a pneumatic conveyance meansconfiguration and the selection of a mass airflow value which ensurethat the filament(s) does not in its transference through the duct meanscome into contact with any inner surface of the duct means.

[0022] Much by preference the cross-sectional shape of the extrudedreconstituted tobacco filament resemble the cross-sectional shape of cuttobacco, particularly cut lamina tobacco. In order to achieve thisresemblance the extruded tobacco filament should be of a substantiallyrectangular or square cross-section. Expansion of the extrudate mayoccur upon exit thereof from the extruder die. Therefore, in a case whenexpansion of the extrudate occurs, in order to provide an extrudedfilament of a rectangular or square cross-section, the exit orifice ofthe die should be of a generally square or rectangular configuration,the sides of the square or rectangle being concave. By use of anappropriate concavity in relation to the degree of expansion of theextrudate there may be produced a filament the cross-sectional shape ofwhich is a substantially straight sided square or rectangle.

[0023] The cross-section of a filament following draw down thereof,advantageously has dimensions of about 0.7 mm×about 1 mm, preferably ofabout 0.3 mm×about 0.8 mm. Suitably the filament has a length,post-cutting, in a range of about 10 mm to about 50 mm. By use of thepresent invention, the beneficial result of a filament of constantcross-sectional dimensions post-draw down is achieved.

[0024] The resultant filamentary reconstituted tobacco product consistsof lengths of a filament comprising a cellular interior and an integralskin extending over, when the filament is of a square or oblongcross-section, at least the four longitudinal sides of the filament.This structure provides a strong product, which product can besubsequently transported pneumatically without being substantiallydegraded.

[0025] The product has a filling value in the range of about 3.8 toabout 5.0 mm³/mg, and may suitably be in the range of about 4.0mm³/mg-about 4.6 mm³/mg. This represents the potential for an increasein filling value of 10-20% over the filling value of products producedin accordance with the processes described in UK Patent SpecificationNos. 2 201 081B and 2 201 080B. The product density may be in the rangeof about 150 mg/mm³ to about 600 mg/mm³, and preferably less than about400 mg/mm³.

[0026] In normal practice, a reconstituted tobacco product manufacturedby means of the present invention will form a proportion of a cigarettefiller blend, other tobacco constituents of which blend may be, orinclude, cut lamina and cut stem.

[0027] Much by preference, a plurality of reconstituted tobaccofilaments are co-extruded. Suitably, when it is the case that aplurality of filaments are co-extruded, a die comprising a plurality ofexit orifices is employed. Preferably, the exit orifices of such anextrusion die are arranged in such a manner that the filaments issuingtherefrom are in a side-by-side, advantageously horizontal, array. It ispreferable that each filament of the plurality of filaments ismaintained out of contact with each of the other filaments. Thus,adherence of the filaments one with another is avoided.

[0028] The present invention also provides an extruder die plate, thedie plate comprising die orifices, the die orifices being of a generallysquare or rectangular configuration, and the sides of the square orrectangle being concave.

[0029] Suitably, the exit face of the die is oblong in configuration andthe exit orifices thereat are arranged in a single row across the face.Alternatively, the exit orifices may be arranged in two, upper andlower, longitudinal rows across the face, the orifices of the upper rowbeing vertically out of registration with the orifices of the lower row.Suitably, when a plurality of filaments is extruded, the duct of thepneumatic conveyance means may be of an oblong cross-section so as toenable the plurality of filaments to travel side-by-side of one anotherthrough the duct. The number of orifices in the die is selected inaccordance with the desired throughput from the extruder.

[0030] Preferably, the extrusion mixture comprises particulate tobacco,starch and binder. Water is preferably added to the above mixture whenthe mixture is in the barrel of the extruder.

[0031] The starch is preferably present in the tobacco/starch/bindermixture at a level within the range of about 5% to about 35% by weightand preferably within a range of about 10% to about 20% by weight. Thestarch is preferably present in the mixture in an amount by weightexceeding that of binder by two times and more preferably by three ormore times. The level of binder in the mixture preferably does notexceed 10% by weight and more preferably does not exceed 5% by weight.

[0032] The starch may, for example, be maize or corn starch. The starch,or a proportion thereof, may be a modified starch.

[0033] Suitably the binder comprises a cellulosic binder. Cellulosicbinder materials for use in practising the present invention may behydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethylcellulose, methyl cellulose and ethyl cellulose. Other binders suitablefor use in practising the present invention include gums, such asxanthan gum, guar gum and locust bean gum. Further suitable bindermaterials will readily occur to those skilled in the art. Binder of themixture may be provided by two or more binder materials.

[0034] Binders of lesser quality, i.e. those which tend to be lessexpensive can be used in the present invention vis-á-vis the highquality binders which are typically required in reconstituted tobaccoproducts as disclosed in GB 2 201 080. Alternatively, lower quantitiesof the high quality binder may be used in the present invention. Therequirement for a lower quality binder and/or a lower quantity of binderfor use in the present invention is predicated upon the fact that theresultant particulate filamentary reconstituted tobacco product of thepresent invention comprises a cellular interior with an integral skinextending over, when the particle is a square or oblong cross-section,at least the four longitudinal sides of the particle. This contrastswith the sheet reconstituted tobacco product of GB 2 201 080 whichcomprises merely an upper skin and a lower skin with a honeycombstructure therebetween.

[0035] Furthermore, as mentioned above the increase in filling valueobtaining with product produced according to the invention provides thepossibility of decreasing the amount of binder in the formulation,whilst maintaining a comparable filling value to the product describedin GB 2 201 080B.

[0036] In addition to tobacco, starch and binder, sugar may be fed tothe extruder. The sugar, if present, may comprise one or more sugars,such for example as fructose, glucose or sucrose. Suitably, the sugar ispresent at a level not exceeding about 5% by weight of thetobacco/starch/binder mixture, but may be present up to a level of about10%.

[0037] Advantageously, the total water present in the extruder is suchthat, without an extrudate drying step being utilised, the moisturecontent of the filament post-draw down is within a range of about 5% to20% by weight (wet basis). By “total water” is meant the sum of anymoisture present in the “dry” components of the tobacco/starch/bindermixture and any added water. Water may be added to one or more of thecomponents of the mixture before the components are fed to the extruderand/or by way of injection via a barrel port(s) of the extruder barrel.A convenient practice is to mix the components of the mixture and thento feed the mixture in a dry or substantially dry state to the extruder,water being added by injection into the extruder barrel.

[0038] Suitably, a humectant and/or plasticiser, such as for exampleglycerol or propylene glycol is fed to the extruder with the componentsof the above referred to mixture and/or by way of injection into theextruder barrel. The inclusion level of the plasticiser may be within arange of about 1 to about 10% by weight on a wet basis.

[0039] Advantageously, filaments with optimised characteristics areobtained by ensuring that the processing within the extruder of thematerials fed thereto takes place adiabatically or close toadiabatically. It is also important to operate with an extruder barreltemperature profile up to the extruder die such that the temperature ofthe tobacco portion of the materials in the extruder does not attain avalue which would be deleterious to the tobacco and is suitably in arange of about 80° Celsius to about 180° Celsius.

[0040] Advantageously, the processing takes place under such conditionsthat immediately upon it issuing from the die, the extrudate is expandedby water therein flashing off to steam. There is thereby effected anincrease in the cross-section of the extrudate and the establishment ofa cellular interior structure.

[0041] As will be readily appreciated by those skilled in the tobaccoreconstitution art, possibilities arise for feeding flavourant materialsto the extruder. Such materials may be nature-identical or artificialflavourants or botanical extracts.

[0042] The particulate tobacco used in the subject inventive process canbe derived from the stem and/or the lamina portions of tobacco leaf, forexample tobacco dust. The particle size of the particulate tobacco ispreferably less than about 500 μm, and is more preferably less thanabout 370 μm. Particle size will usually be determined by the smallestdimension of the die orifice.

[0043] In order that the present invention may be clearly understood andreadily carried into effect reference will now be made, by way ofexample, to the diagrammatic drawings hereof, in which:

[0044]FIG. 1 shows an apparatus suitable for carrying out the method ofthe present invention;

[0045]FIG. 2 shows an alternative apparatus suitable for carrying outthe method of the present invention; and

[0046]FIG. 3 shows a view of the front face of an extrusion die and theexit orifices thereof.

[0047] Wherever possible reference numerals in respect of each part ofthe apparatus shown in the figures have been conserved between thefigures.

[0048] As shown in FIG. 1, the apparatus 1 comprises a twin-screwextruder 2 (manufactured by APV Baker, of Peterborough, U.K., underModel designation number MPF50-15) including a die 3 and a barrel 4. Theextruder die 3 is mounted at the outlet end of the barrel 4 of theextruder 2. A steam extraction unit 5 is located above the extruder die3 and is operable to remove steam issuing from the die 3 during theextrusion process. The apparatus 1 further comprises pneumaticconveyance means including a gaseous medium (i.e. air) duct means 6extending from a position adjacent to the extruder die 3, and gaseousmedium transfer means 8. As may be seen from FIGS. 1 and 2, the ductmeans 6 comprises at the upstream end thereof a curved inlet portion 6′.The duct means 6 is of an oblong cross-section, the major dimension ofthe cross-section extending perpendicularly to the view depicted inFIG. 1. The gaseous medium transfer means 8 comprises suction meansprovided by a suction fan. A cool air intake port 9 is in communicationwith the duct means 6 at the lower end thereof, which air intake port 9is operable to allow cooling air to be drawn into the duct means 6. Acutting means 10, i.e. a rotary cutter, is situated in the duct means 6and is operable to cut the extruded reconstituted tobacco filaments 7into particles of filamentary reconstituted tobacco product 12.Incorporated in the duct means 6 is a particle/air separator 11 wherebyair flowing through duct means 6 is separated from the particles offilamentary reconstituted tobacco product 12 and any other particulatematter being conveyed through the duct means 6. The filamentary tobaccoproduct 12 is conveyed through an air lock 13, i.e. a rotary air lock,to feed means 14, which feed means 14 conveys the filamentary tobaccoproduct 12 to a silo (not shown).

[0049] In FIG. 2 an alternative apparatus to that of FIG. 1 is shown,wherein the duct means 6 is orientated such that the filaments 7 aretransferred in a direction longitudinal of the filaments 7 away from thedie 3 in a substantially horizontal plane. This contrasts with theapparatus 1 of FIG. 1 in which the duct means 6 is orientated such thatthe filaments 7 are transferred, at least over a portion of the ductmeans 6, in a substantially vertical plane. The apparatus of FIG. 2otherwise resembles that depicted in FIG. 1 excepting that in FIG. 2 theapparatus 1 comprises a storage container 15, in to which container 15,in operation of the apparatus 1, cut product 12 is pneumaticallyconveyed.

[0050] A view of the front face 3′ of the die 3 is shown in FIG. 3. Asan be seen from FIG. 3, the die 3 is provided with a plurality of exitorifices 16, 16′. Only a small number of exit orifices 16, 16′ have beendepicted in FIG. 3. However, the die 3 is, in fact, provided with atotal of about one hundred exit orifices 16, 16′. Thus, a plurality ofreconstituted tobacco filaments 7 are co-extruded. Each exit orifice 16,16′ of the die 3 is of a generally square or rectangular configuration,the sides of the square or rectangle being concave. By use of anappropriate concavity in relation to the degree of expansion of theextrudate upon exit thereof from the die 3, there may be producedfilaments 7 the cross-sectional shape of each being a substantiallystraight sided square or rectangle. The exit orifices 16, 16′ of the die3 are arranged in such a manner that the filaments 7 issuing therefromare in a side-by-side, horizontal array. Each filament 7 of theplurality of filaments 7 is maintained out of contact with each other ofthe filaments 7. The die 3 is of oblong configuration and the exitorifices 16, 16′ are arranged in two, upper and lower, longitudinal rowsacross the face 3′. The orifices of the upper row 16 are vertically outof registration with the orifices of the lower row 16′, as can be seenfrom FIG. 3.

[0051] In operation of either of the FIG. 1 or the FIG. 2 apparatus adry mixture of 80% particulate tobacco dust, 15% starch and 5%cellulosic binder is fed at a rate of about 145 kg/hour to the extruder2. A feed unit (not shown) of the extruder 2 serves to feed the mixturethrough a feed pipe (not shown) to the inlet end of the barrel 4 of theextruder 2. Water drawn from a tank (not shown) is injected at a rate ofabout 21 kg/hour into the barrel 4 under the action of a pump (notshown). Similarly, glycerol is drawn from a further tank (not shown) andis injected into the barrel 4 at a rate of about 5 kg/hour. The totalwater in the wet mix in the barrel 4 may, for example, represent 16% byweight of the wet mix.

[0052] The barrel 4 is provided with heating means (not depicted) by theoperation of which a desired temperature profile can be maintained alongthe barrel 4. The barrel temperature may, for example, be maintained at40° Celsius at the inlet end increasing to 95% Celsius at the outletend.

[0053] The pressure within the extruder is maintained at a high enoughvalue to ensure that water therein remains in the liquid phase. Apressure within the range of 500 psig (3,400 kPa or 34.5 Bar) to 2000psig (13,600 kPa or 137.8 Bar) may thus be used, such as 1000 psig(6,800 kPa or 68.9 Bar) to 1500 psig (102,000 kPa or 103.4 Bar).

[0054] At these temperatures and pressures the starch fed to theextruder 3 is caused to gelatinise.

[0055] As the extruded filament 7 issues from the plurality of exitorifices 16, 16′, water therein flashes off to steam, as a result ofwhich the cross-sectional shape of each filament changes due toexpansion, such that the resultant cross-sectional shape of eachfilament 7 is a substantially straight sided square or rectangle whenthe shape of each exit orifice is as that shown in FIG. 3.

[0056] The approximately 100 co-extruded filaments 7 issue from the die3 at a total mass rate of about 157 kg/hour, the linear speed of eachextruded filament 7 being about 1 metre/second. The steam extractionunit 5 removes the flashed off steam.

[0057] The filaments 7 issuing from the orifices 16, 16′ are directedinto the duct means 6 and are transferred through the duct means 6 in adirection longitudinal of the filaments 7 away from the die 3. Uponentry of the filaments 7 into the duct means 6, the filaments 7 becomeentrained in a continuous stream of air flowing through the duct means6. Thus the filaments 7 are pneumatically conveyed through the ductmeans 6. The airflow in the duct means 6 is effected by the suction fan8. During conveyance of the plurality of filaments 7 in the oblong ductmeans 6 each filament 7 of the plurality of filaments 7 is maintainedout of contact with each other of the filaments 7. Thus, adherence ofthe filaments 7 one with another is avoided.

[0058] The filaments 7 are drawn down to reduce the cross-sectionaldimensions thereof. The draw down is effected as a result of thevelocity of the air flowing in the duct means 6 being greater than theextrusion velocity, which velocity differential engenders a drag forceof the air on each of the filaments 7. Therefore, the filaments 7downstream of the extruder die 3 are tensioned and thus drawn down bythe air. By way of example, a velocity of the airflow which is effectiveto tension and draw down the filaments 7 is in the range of about 60metres/second to about 180 metres/second when the extrusion velocity isabout 1 metre/second. Such an airflow velocity is provided at least atan initial portion of the duct means 6, in order to effect draw down ofthe filaments 7 issuing from the orifices 16, 16′ of die 3. Draw down ofthe filaments 7 is effected until the required cross-sectional size ofthe filaments 7 is reached. The velocity of the airflow in the ductmeans 6 downstream of the initial draw down portion of the duct means 6is suitably at least 35 metres/second, and may be about 50-60metres/second. This reduction in airflow velocity is achievable byarranging that downstream of the draw down portion of the duct means 6,the cross-sectional area thereof is greater than at the draw downportion. A downstream airflow velocity such as 35 metres/second issuitable for transporting the filaments 7 without substantial draw downthereof. Thus the cross-sectional dimensions of the filaments 7 remainconstant following the draw down step. The filaments 7 subsequent todraw down are conveyed at a rate of, for example, about 2 metres/second.

[0059] The filaments 7 are cut transversely at intervals of about 30 mmalong the length thereof by the cutting means 10 thus to provide aproduct 12 constituted of filamentary particles of reconstitutedtobacco. This cutting step takes place subsequent to the reduction inthe cross-sectional dimensions of the filaments 7. The particulateproduct 12 is then pneumatically conveyed at about 20 metres/secondeither to an air lock 13 (FIG. 1) or directly to a storage container 15(FIG. 2). Silo feed means 14 may be situated downstream of the air lock13. The particles of the product 12 and the conveying air are separatedby way of an air/particle separator 11.

[0060] The method may further comprise an enhanced cooling step, wherebycooling air is brought into contact with the extruded filament 7 toeffect cooling thereof. The cooling air enters the duct means 6 throughthe cool air intake port 9. If deemed appropriate a plurality of coolair intake ports may be provided. Suitably, the cross-sectional area ofthe bore of the cool air intake port 9 is the same as that of the boreof the inlet portion 6′ of the duct means 6. Advantageously, the sum ofthe cross-sectional area of the intake port 9 and that of the inletportion 6′ is equivalent to the cross-sectional area of the run of theduct means 6 extending immediately downstream of the inlet portion 6′.Preferably, the air flow through the cooling air intake port 9 isadjustable; for example a position adjustable baffle (not shown) may belocated in the cooling air intake port 9, which baffle is operable tovariably control the air flow rate through the intake port 9.Advantageously, the temperature of the filaments 7 at the cutting means10 should be low enough to ensure that the extrudate does not foul thecutting means 10. The temperature of the filaments 7 at the cuttingmeans 10 should be between 30° and 50° Celsius.

[0061] By way of example, the cross-sectional area of each of the intakeport 9 and the inlet portion 6′ of the duct means 6 is in the range ofabout 10 cm² to about 20 cm², the cross-sectional area of the duct means6 at the aforementioned initial draw down portion thereof is in therange of about 20 cm² to about 40 cm², and the cross-sectional area ofthe duct means 6 at the cutting means 10 is in the range of about 250cm² to about 400 cm².

[0062] The cross-section of each filament 7, following draw downthereof, has dimensions of, for example, about 0.7 mm×about 1 mm. Theparticles of filamentary tobacco product 12 (i.e. the portions of thefilament 7 post-cutting) are each of a length, for example, in the rangeof about 30 mm. The resultant filamentary reconstituted tobacco product12 consists of particles each of which particles 12 is constituted by alength of a filament 7 and thus comprises a cellular interior and anintegral skin extending over, when the particle is of a square or oblongcross-section, at least the four longitudinal sides of the particle.

[0063] The extruder may be any extruder suitable to provide a range ofthroughputs. The throughput may be up to 300 kg/hr, a suitable extruderfor which throughput being the Bühler DNDG 62. Increasing the throughputof the extruder will require consequential increases in the gaseousmedium transfer means, such as an increase in power of the suction fanup to about 75 kW-about 100 kW for a throughput of up to about 300kg/hr. A throughput of about 150 kg/hr would require a suction fan ofabout 45 kW.

[0064] In an alternative arrangement of the subject invention thepneumatic conveyance means may additionally comprise pneumatic jetmeans. It is preferred that the pneumatic jet means are located adjacentto the extruder barrel such that when the filament emerges from the dieorifice the filament is readily transferred in a direction longitudinalof the filament away from the die under the action of the continuousflow of gaseous medium provided by the pneumatic jet means, into and orthrough the duct means.

[0065] Alternatively, the pneumatic conveyance means may comprisecompressed air jets. In this alternative arrangement of the subjectinvention, compressed air may be delivered from the compressed air jetsin controlled pulses or as a continuous flow such that when the filamentemerges from the die orifice, the filament is transferred in a directionlongitudinal of the filament. The compressed air may be delivered so asto separate the filaments from one another and to transfer the filamentsin a side-by-side array. It is preferred that the compressed air jetsare arranged relative to the barrel of the extruder so as to providecompressed air substantially tangentially to the filament flowdirection. Alternatively the compressed air jets may be arranged so asto deliver air through the die plate by means of at least one dieorifice. It is preferred that the die orifices are other than thosethrough which the filaments are extruded.

[0066] In a further alternative arrangement of the subject inventionusing compressed air jets the pneumatic conveyance means may optionallycomprise the duct means.

[0067] The compressed air jets may be so arranged as to provide meansfor breaking the filaments into discrete elements of a controllable sizeand transferring the elements away from the die orifice.

[0068] In the arrangements of the subject invention using compressedair, the air is supplied at a pressure in the range of about 1 to about200 bar, and is preferably in the range of about 5 to about 10 bar.

1. A method of handling an extruded reconstituted tobacco filamentdownstream of die means through which said filament is being extruded,wherein said filament is transferred in a direction longitudinal of saidfilament away from said die by pneumatic conveyance means, saidconveyance means effecting draw down of said filament such that thecross-sectional dimensions of said filament are reduced.
 2. A methodaccording to claim 1, wherein said extruded filament is cut transverselyat intervals along the length thereof into a plurality of elements.
 3. Amethod according to claim 2, wherein said elements are cut at intervalsin the range of about 10 mm to about 50 mm.
 4. A method according toclaim 2 or 3, wherein said extruded filament is cut subsequent to thereduction in the cross-sectional dimensions of said filament.
 5. Amethod according to any one of claims 2-4, wherein cutting meansutilised in the cutting step is a rotary cutter.
 6. A method accordingto any one of the preceding claims, wherein cooling air is brought intocontact with said extruded filament to effect cooling thereof.
 7. Amethod according to claim 6, wherein the temperature of said extrudedfilament when cut is within the range of about 20° to about 60° Celsius.8. A method according to claim 7, wherein said temperature is in therange of about 30° to about 50° Celsius.
 9. A method according to anyone of the preceding claims, wherein said pneumatic conveyance meanscomprises gaseous medium transfer means and duct means, said transfermeans being operable to cause transfer of a gaseous medium, as acontinuous flow through said duct means.
 10. A method according to anyone of the preceding claims, wherein the transfer in a directionlongitudinal of said filament is initially perpendicular to the die faceof said die means.
 11. A method according to claim 10, wherein after thetransfer perpendicular to the die face, the transfer is in asubstantially horizontal or vertical plane.
 12. A method according toany one of the preceding claims, wherein draw down of said filament iseffected by the velocity of the gaseous medium flowing in a directionwhich corresponds with the transfer direction of said filament beinggreater than the extrusion velocity.
 13. A method according to claim 12,wherein said velocity of said gaseous medium is in the range of 60-180m/s.
 14. A method according to claim 13, wherein said velocity is atleast 100 m/s.
 15. A method according to any one of claims 11-13,wherein the draw down of said filament is enhanced by tensioning saidfilament further by drawing said filament over tensioning means.
 16. Amethod according to claim 14, wherein said tensioning means is a drivenroller.
 17. A method according to any one of the preceding claims,wherein the conveying velocity after draw down of said filament is inthe range of 30-60 m/s.
 18. A method according to claim 17, wherein saidconveying velocity is at least 35 m/s.
 19. A method according to claim18, wherein said conveying velocity is in the range of 40-60 m/s.
 20. Amethod according to any one of claims 9-19, wherein a pneumaticconveyance means configuration and a mass airflow valve are selectedsuch that said filament(s) does not, in its transference through saidduct means, come into contact with any inner surface of said duct means.21. A tobacco filament made in accordance with the method of any one ofclaims 1-20, wherein said extruded tobacco filament is of rectangular orsquare cross-section.
 22. A tobacco filament made in accordance with themethod of any one of claims 2-21, wherein the cross section of saidfilament following draw down thereof, has dimensions of about 0.7 mm byabout 1 mm.
 23. A tobacco filament according to claim 22, wherein saiddimensions are about 0.3 mm by about 0.8 mm.
 24. An extruder die platecomprising die orifices, said die orifices being of a generally squareor rectangular configuration, and the sides of the square or rectanglebeing concave.
 25. An extruder die plate according to claim 24, whereinsaid die orifices are arranged in such a manner that the extrudedfilaments issuing therefrom are in a side-by-side array.
 26. An extruderdie plate according to claims 23 or 24, wherein the exit face of saiddie plate is oblong in configuration and the exit orifices thereof arearranged in a single row across the face.
 27. An extruder die plateaccording to claims 23 or 24, wherein the exit face of said die plate isoblong in configuration and the exit orifices thereat are arranged intwo, upper and lower, longitudinal rows, the orifices of the upper rowbeing vertically out of registration with the orifices of the lower row.28. An extruded reconstituted tobacco filament, wherein said filament isof a substantially rectangular or square cross-section.
 29. An extrudedreconstituted tobacco filament according to claim 23, comprising acellular interior and an integral skin extending over at least the foursides of said filament.
 30. An extruded reconstituted tobacco filamentaccording to claim 28 or 29, wherein the cross-section of said filamenthas dimensions of about 0.7 mm by 1 mm.
 31. An extruded reconstitutedtobacco filament according to claim 30, wherein said dimensions areabout 0.3 mm by about 0.8 mm.
 32. A filamentary reconstituted tobaccoproduct consisting of lengths of a filament comprising a cellularinterior and an integral skin extending over, when the filament is of asquare or oblong cross-section, at least the four longitudinal sides ofthe filament.
 33. A filamentary reconstituted tobacco product accordingto claim 32, wherein said product has a filling value in the range ofabout 3.8 to about 5.0 mm³/mg.
 34. A filamentary reconstituted tobaccoproduct according to claim 33, wherein said filling value is in therange of about 4.0 mm³/mg to about 4.6 mm³/mg.
 35. A filamentaryreconstituted tobacco product according to any one of claims 32-34 andhaving a density in the range of about 150 mg/mm³ to about 600 mg/mm³.36. A filamentary reconstituted tobacco product according to claim 35,wherein said density is less than about 400 mg/mm³.
 37. A methodaccording to any one of claims 1-20, in conjunction with an extruder dieplate of any one of claims 24-27, wherein the concavity of said orificesof said die plate is such that there is produced a filament, thecross-sectional shape of which is a straight-sided square or rectangle.38. A method according to any one of claims 1-20 or claim 37, wherein aplurality of reconstituted tobacco filaments are co-extruded by means ofa die comprising a plurality of exit orifices.
 39. A method according toclaim 37 or 38, wherein the exit orifices of said die are arranged insuch a manner that the filaments issuing therefrom are in a side-by-sidearray.
 40. An extruded filamentary tobacco pneumatic conveyance meanscomprising in combination gaseous medium transfer means and duct means,the transfer means being operable to cause transfer of gaseous medium,as a continuous flow thereof, through the duct means, and an extrudercomprising a die plate arranged to produce a plurality of filaments,wherein the inlet end of said duct means is positioned adjacent to saidextruder die plate such that when said filaments emerge from the dieorifice, said filaments are readily transferred in a directionlongitudinal of said filaments away from said die plate under the actionof said continuous flow of gaseous medium through said duct means,wherein a plurality of filaments are able to travel side-by-side of oneanother through said duct, said conveyance means effecting draw down ofsaid filament such that the cross-sectional dimensions of said filamentare reduced.
 41. An extruded filamentary tobacco pneumatic conveyancemeans according to claim 40, wherein said inlet end of said duct meansis located within about 5 mm-20 mm from said extruder die.
 42. Anextruded filamentary tobacco pneumatic conveyance means according toclaim 41, wherein said inlet end of said duct means is located withinthe range of about 10 mm-about 15 mm from said extruder die.
 43. Anextruded filamentary tobacco conveyance means according to any one ofclaims 40-42, wherein said side-by-side arrangement is horizontal. 44.An extruded filamentary tobacco pneumatic conveyance means according toany one of claims 40-43, wherein said duct means has an oblongcross-section suitable to allow a plurality of filaments to travelside-by-side of one another through said duct.
 45. An extrudedfilamentary tobacco pneumatic conveyance means according to any one ofclaims 40-44, wherein said die plate is that of claims 24-27.
 46. Asmoking article comprising a filamentary reconstituted tobacco productaccording to any one of claims 32-36.